Process of metal deposition and product thereof



Patented Aug. 15, 1933 UNITED" STATES PROCESS OF METAL DEPOSITION AND PRODUCT THEREOF James B.'Grenagle, Baltimore, Md., assignor of one-half to William W. Varney, Baltimore, Md., and one-half to Universal Alloys, Incorporated, Baltimore, Md-,

Maryland a Corporation of No Drawing. Application March 1, 1930 Serial No. 432,566

The objectof my invention is the deposition of metals by electrolysis from salts thereof in an electrolyte oxygen free or substantially so.

5 ing of tantalum.

A further object of my invention is tantalate substance.

A further object of my invention is the process of plating tantalum.

With the foregoing and other objects in view, my invention consists of the methods employed, combination and arrangements of systems, elements and means as hereinafter described and set forth, but it is understood that changes, variations and modifications may be resorted to which come within the scope of the claims hereunto appended.

To illustrate my new process, I will first give a specific example in detail of the operation of my invention and the product obtained therefrom as applied to the element tantalum.

By my method of obtaining tantalum I obtain tantalum capable of being soldered for the reason that it has not undergone the slightest trace of oxidation on the surface. It may be soldered by employing iron solders generally employed in industrial purposes, such as, zinc chloride.

In soldering, it is desirable to protect against oxidation by covering the surface with a layer ing protection.

I have discovered a cold process for obtaining an electric deposit of tantalum and other metals.

To more fully understand my invention, It will state a few well known facts leading up to my discovery. When a suitable electric current is passed into or through an aqueous solution of a binary salt of a very oxidizable metal (NaCl for example), such salt is decomposed, the chlorine passing to the positive pole, the sodium, however, by reason of its affinity for oxygen, oxidizes in contact with water in proportion as it is released, to form soda or oxide of sodium. Similar is the case with tantalum, and many other metals, when a solution of the chloride of the metal, as the example given, tantalum is decomposed by the electric current.

My invention in this case illustrated is the electrolysis of the chloride of tantalum at a relatively low temperature, r ecovering the tantalum and preventing the oxidation of the tantalum as it is liberated. In order todo this the chloride of tantalum is dissolved in a solvent which does not contain even a molecule of oxygen. This solvent is preferably a fatty or aromatic hydroof paraffin or other suitable varnish as a solder- 3 Claims. (01. 204-1) carbon of a nitrite or other nitrogen compound, but other compounds may be used if they do not contain oxygen. A further object of my inventionis the depositr It must be noted that liquids into the composition of which only nitrogen and carbon enter are 7 generally very poor conductors of electricity and do not allow the current to pass, or require such a high voltage that the operation would be impracticable. It has been found that it is possible to facilitate the passage of the electric current in or through bodies of the fatty or aromatic series, and I have selected those which are good solvents of tantalum chloride, for example toluene, by adding thereto other substances the presence of which facilitates the passage of the electric current, such as bifluoride of potassium acid fluoride KHFz, say about 1%. Other alkali fluorides and bifluorides, both fixed and volatile, may be employed. 'While some of the substances employed may contain oxygen, it is not to such an extent as to materially affect the process.

It is desirable that the strength of the electrolytic bath be maintained constant, and to that end a paste of tantalum chloride such as TaClr, and carbon preferably lampblack is formed and moulded into loaves which are dried in a kiln heated to red heat. The chlorine, obtained by the electrical decomposition of sodium chloride, is passed over these loaves while hot, and the chloride of tantalum formed thereby will melt; this enables me to reduce tantalum chloride (TaCls) to probably a binary compound (TaClz), an unstable compound, but soluble in the electrolyte used with probably a protecting element of carbon tetrachloride. But this is speculative; the only thing I can state is what I did and what happened as the result thereof. It is moulded, pulverized and dissolved, in the toluene or other solvent substantially free of oxygen; this forming the electrolytic bath from which the tantalum is abstracted as a metal by the electric decomposition taking place. The tantalum thus obtained is oxygen free.

As it is desirable to keep the bath at required strength, this can be done by any well known means, such as constant renewal from an outside supply, or the addition of pulverized maor plating, or a solid covering thereof; a higher current being used if a metallic powder of greater or less tenuity is desired, such .as might be required for certain purposes such as metallic painting, or for use in accumulators, electric batteries, or entering into the composition of explosives. For example, the electrolyte-may'consist of an aliphatic compound such as acetonitrile or any compound substantially free of oxygen,

' stable at normal temperature and ordinary atter of cathode surface .gives an adequate deposit,

and that from 8 to -10 amperes gives a non adherent or powder deposit. Whenthe poles are about 4 to 5 cm. apart, the voltage may befrom 3 to 5 volts. The anode from which the current passes should be of a conducting substance not attacked by the electrolyte. I have found carbon to be a suitable electrode in the example given. The cathode or pole upon which the metal is deposited, or upon which the current enters from the electrolyte, may consist of almost any conducting surface, preferably one not attacked by the electrolyte. For that also I have found scatbon to be a satisfactory pole upon which to deposit; but as herein stated, the elements iron, copper and other metals may be used where a plating is desired.

I have found that the application of this process may be applied toalmost any conducting surface, whether metal or not,- and.th at it will deposit on almost any metal that maybe introduced into the bath; especially is it adapted for depositing on iron, copper, or alloys of these metals.

In the above I have described specific elements, but I do not wish to be limited to those mentioned. I have suggested acid fluoride of potassium (KHFz) for inducing the passage of the electric current, but there are other equivalent substances Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1'. The process of forming a solution of tantalum content for use in the process of claim 2 consisting of treating tantalum chloride (TaCls) in a paste with carbon heated to a red heat, and while so heated contacting chlorine gas therewith,- then dissolving the same in an acetonitrile bath whereby a solution of tantalum is obtained.

2. The process of producing tantalum by electrolyzing an acetonitrile bath comprising potassium bifluoride and anhydrous tantalum chloride. 3. The process of producing tantalum by electrolyzing'an acetonitrile bath comprising 1% potassium bifluoride and 10% anhydrous tantalum chloride.

JAMES B. GRENAGLE. 

